Tension regulator for sewing machine presser bar



A SHUMAN May 14, 1963 TENSION REGULATOR FOR SEWING MACHINE PRESSER BARFiled Dec. 27, 1960 INVENTOR.

SH U M AN ABRAHAM ATTORNEY 3,089,447 TENSION REGULATOR FOR SEWINGMACHINE PRESSER BAR Abraham Shurnan, Union Mill No. 1, Fall River, Mass.Filed Dec. 27, 1960, Ser. No. 78,511 1 Claim. (Cl. 112-435) My presentinvention relates to sewing machines and more particularly to a devicefor regulating the tension on the presser foot.

The principal object of the present invention is to provide a calibrateddevice for presetting the tension on the presser foot of a sewingmachine.

A further object of the present invention is to provide a tensionregulator which permits a uniform tension to be applied to a pluralityof machines doing the same work.

Another object of the present invention is to provide a tensionregulating device which can be simply and easily adjusted by theoperator of the sewing machine.

A further object of the present invention is to provide a presser foottension regulator which is simple in construction and easy andeconomical to manufacture and assemble.

With the above and other objects and advantageous features in view myinvention consists of a novel arrangement of parts more fully disclosedin the detailed description following in conjunction with theaccompanying drawings and more particularly defined in the appendedclaim.

In the drawings,

FIG. 1 is a perspective view of a presser foot bar assembly with thetension regulator of the present invention.

FIG. 2 is an enlarged perspective view of the regulating device.

In commercial dressmaking operations the average factory is equippedWith a large number of sewing machines sometimes running into hundreds.The quality of the stitching depends on the skill of the operator andthe proper setting on the machine. Adjustments are made for the precisenumber of threads per inch. However, while the machine is equipped withmeans for loosening or tightening the pressure on the presser foot, mostoperators have little or no knowledge of how to use it. The pressuremust be varied with the thickness and type of material passing throughit. As a result the pressure settings are never uniform and one operatorwill sew a portion of a garment with one pressure setting while a secondoperator will sew another portion of the same garment with a differentsetting. This causes a variation in the stitching.

No sewing machine on the market has any means for accurately fixing thesetting. The present invention is designed to provide the sewing machinewith means for presetting the presser foot pressure. By notifying theoperators of the several machines that the particular material beingworked on requires a certain pressure, the device of the presentinvention permits the operator to simply and easily adjust the machineto the required pressure.

While the presser foot bar construction of various makes of sewingmachines vary in minor details, they all use essentially the same basicprinciple. The presser foot is mounted at the bottom end of a verticalbar which is retained adjacent its top end in a guide bracket. The upperend of the presser foot bar is hollow. At the top of the sewing machinehead a bolt is threaded into place which rides on a small shaft whichextends downwardly into the hollow presser foot bar. A tension springsurrounds the shaft with its upper end against the bolt and its lowerend against the top edge of the pressure foot Patented May 14, 1963 baror holding collar. When the presser foot is lifted the collar and barare lifted against the action of the spring and the bar telescopes overthe shaft. When the presser foot is dropped the spring tension pushesthe bar downwardly and it is this tension which produces the pressure ofthe presser foot on the cloth over the feed dog. The present inventionprovides a calibrated adjustment for the tension of the spring.

For purposes of illustration I have shown the device mounted on the typeof assembly used on a Singer sewing machine. In this construction thesewing machine head 11) shown in dotted lines in FIG. 1 houses theneedle reciprocating and the presser foot mechanisms. The presser foot11 may be of any conventional design and is mounted on the bottom end ofthe presser foot bar 12. The upper end of the presser foot bar 12comprises a hollow cylindrical portion 13 which extends through a guidebracket 14. The bracket 14 is locked to the hollow portion 13 and movesvertically with it. A shaft 15 is mounted in axial alignment with theportion 13 and is adapted to telescopically slide into it. The tensionspring 16 surrounds the shaft 15. The bottom end of the spring 16 restson the upper edge of the guide bracket 14. The top of the spring 16 andthe top of the shaft 15 bear against the bottom of the adjustment device17 shown in FIGS. 1 and 2. In some constructions the shaft 15 is madeintegrally with the adjustment device 17. The device 17 consists of anelongated threaded bolt 18 with very fine threads. One side of the bolt18 is flattened at 19. The top of the bolt 18 is provided with a fingergripping portion 20'. With this construction turning movement of thebolt 18 downwardly increases the tension of the spring 16 and turningmovement of the bolt 18 upwardly decreases the tension of the spring.The spring tension is uniform throughout the different models of themachines because the same spring 16 in the same length is used on allthese machines. The flat portion 19 is now subdivided with three lines21 marked light, medium and heavy. The calibration or spacing of thelines 21 should be such that from the lowest line to the intermediateline, which is light will run from 3 pounds to 7 pounds pressure on thepresser foot. The medium calibration runs from 7 to 12 pounds pressureand the heavy runs from 12 to 15 pounds pressure. The threaded portionof the bolt 18 is approximately 1 /2 inches in length and the variouscalibrations are approximately /3 of an inch apart. It will be foundthat this size will produce substantially the same pressure for everymachine for the same setting.

In use a locking indicator collar 22 is provided with internal threads23 which ride on the bolt :18. The upper edge of the collar 22 isbevelled at 24 for easier reading. In setting the proper tension thebolt 18 is turned upwardly to its topmost position. The collar 22 is nowrotated until its top bevelled edge 24 indicates the desired pressure.The operator now grasps the portion 20 and rotates the bolt clockwiseand downwardly until the collar 22 reaches the top of the sewing machinehead 10 at which point it looks the assembly in place. It will be foundthat the spring tension 16 will then be maintained at the indicatedpressure. Now when a new material is being passed through the shop theoperators can be notified to use a certain size needle, with so manythreads to the inch and with a particular pressure. Since the pressureadjustment is simple and easy to make no mechanic is required. Theresult will be complete uniformity in the stitch for the particularmaterial for the garment regardless of the machine used.

In existing machines the adjustment bolt is removed and replaced withthe device of the present invention. This can be done externally withoutdismantling the sewing machine head. Thus the device is simple and easyto manufacture and economical to install. Other advantages of thepresent invention will be readily apparent to a person skilled in theart.

I claim:

In a sewing machine head, a vertical presser bar having a hollow portionat its upper end and a presser foot mounted at its lower end, a shaftmounted axially with said presser bar and having its lower endtelescoping into the hollow portion of said presser bar, a bracketlocked to the upper end of said hollow portion and vertically movabletherewith, a tension spring surrounding said shaft and bearing againstthe upper edge of said bracket, and means for applying a predeterminedtension to said spring, said means including a bolt threaded verticallyinto the sewing machine head, the lower end of said bolt engaging theupper ends of said shaft and said spring, said bolt extending verticallyfrom the sewing machine head, said bolt having a longitudinal flattenedportion with calibrations to permit a reading of the setting of saidbolt and spring tension, a collar threadedly mounted on said bolt forlocking said bolt in predetermined tensioning position, said collarhaving an upper edge cooperating with said calibrated portion of saidbolt whereby said collar designates the desired position of said bolt.

References Cited in the file of this patent UNITED STATES PATENTS820,290 Drysdale May 8, 1906 2,892,429 Fischbein June 30, 1959 FOREIGNPATENTS 795,634 Great Britain May 28, 1958 803,960 Great Britain Nov. 5,1958

